Expansible chamber devices – Oscillating working member or cylinder therefor
Patent
1994-12-09
1996-03-05
Denion, Thomas E.
Expansible chamber devices
Oscillating working member or cylinder therefor
92 136, 92128, F01C 900
Patent
active
054957915
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a fluid-operated actuator comprising a chamber part with at least one chamber which can be supplied with a pressurized fluid, a carrier which is mounted in the chamber part in such a manner that it can rotate about an axis of rotation, and which can be connected with an object which has to be rotated, and a plunger piston whose longitudinal axis extends in the form of a circular arc, and whose axis, which extends through the centre of the circle and perpendicular to the circle plane, is coincident with the axis of rotation of the carrier, which plunger piston is arranged to be rotated about the axis of the rotation, and extends in the chamber, and to be connected with the carrier, where the plunger piston via a sealing device is passed sealingly through an opening in the chamber, and there is clearance between the surface of that section of the plunger piston which is located in the chamber and the chamber walls.
Actuators of this type can be used for the control and operation of valves and the like, for the operation of control organs in aircraft, as steering engines etc. However, such actuators have encountered difficulty in absorbing the large radial forces which are exerted without elastic deformation of the plunger piston and thereby its faulty positioning in relation to adjacent parts. Such deformation or faulty positioning can result in a deterioration in the efficiency of the parts and permanent damage to the chamber part or the plunger piston.
From EP 0098 614 there is known an actuator of the type which is mentioned in the introduction, wherein the forces which are caused by the hydraulic pressure and exerted against the piston, are counteracted by the carrier alone. The piston therefore will be exposed also to large bending moments. In addition to this unfavorable loading of the piston the resulting deflection of the piston makes a complicated, movable sealing device necessary at the places where the piston is introduced into the chamber part.
From U.S. Pat. No. 3,444,788 it is known that the plunger piston may be extended outside the chamber part in order to form a complete circular arc. Furthermore the plunger piston is designed as part of a central carrier part. In this case the radial forces are absorbed by the carrier part and special bearing elements provided in the cylinder part. However, a design of this kind is encumbered by the disadvantage that it has very limited working range. Moreover the carrier part is fixedly connected with the plunger piston, which causes problems during assembly and dismantling and when the actuator has to be connected to valve spindles which may be of varying length and diameter.
According to the applicant's Norwegian Patent No. 133 678 another device is known for absorbing and compensating for the large forces which can be exerted. A piston rod in the form of a circular arc with a rectangular cross section is connected with a short piston with a rectangular cross section. The piston is provided inside a cylinder which also has a rectangular cross section and which extends along a circular arc of 180 degrees. The piston rod extends outside the cylinder housing from one side of the piston to the other side thereof. In order to absorb and compensate for the radially exerted forces and thereby avoid destructive wear and tear, due, amongst other things, to the piston rod coming into contact with the end piece of the cylinder space, and to prevent the piston from seizing up, two opposite sides of the rectangular piston rod are provided in such a manner that they slide against two adjacent supporting walls in the cylinder space. By this means a large supporting surface and the possibility of transferring large motive forces is obtained. The cylinder space, the piston and the piston rod, however, have to be produced with extremely small tolerances, a process which is expensive and involves demanding work.
The object of the invention is to provide an actuator of the type described in the introduction which is not encumbered by the above-menti
REFERENCES:
patent: 2657538 (1953-11-01), Myers
patent: 2936636 (1960-05-01), Wacht
patent: 2996049 (1961-08-01), Huska
patent: 3070075 (1962-12-01), Hanselmann
patent: 3444788 (1969-05-01), Sneen
Heim Edgar J.
Sande Kurt
Staaland Torbjorn
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